JOE'S VALLEY, Emery County — The top of the dinosaur's bone was about the size and shape of a serving platter.
The animal's shocking bulk became obvious when the paleontologist said that actually, it was "a very well-preserved vertebra."
This may be Utah's first Tyrannosaurus rex. If it is not, it is an equally large and previously unknown carnivorous beast from the last days of the dinosaurs. Either way, it is one of Utah's the most exciting dinosaur discoveries in decades.
This week, the Deseret News joined Mike Getty, collections manager for paleontology at the Utah Museum of Natural History, and Mark Loewen, a University of Utah graduate student in geology, on a dinosaur dig in the Manti-LaSal National Forest.
Their base camp is near Joe's Valley Reservoir. To reach the dig, they drive up a steep dirt road, walk across rangeland and into forests, hike through gullies, scramble on rock ledges and climb towering gravelly hills. The dig is at 8,500 feet elevation.
For most of the excavation, which started on June 1, volunteers helped with the hard work of pickaxe and shovel to burrow through a slope of mudstone and sandstone. But this day, the volunteers were helping at another site.
The potential T. rex bones were emerging from a pit about 20 feet by 8 feet. Overburden removed varied from a few inches to 6 feet deep.
"We moved several tons of rock," said Getty.
In the early or middle 1990s, a geology graduate student and a technician from the geology department were in the region studying the ancient sediments. The student had car trouble. Meanwhile, the technician looked around the hills and noticed fossils.
"There were a few bones eroding out, broken up on the surface," Getty said. Later, bones were collected from the surface.
"They went in a little bit to the hill and just got the ones which were near the surface," he added. "Because the bones were very large, they thought it was a sauropod."
Sauropods were huge plant-eating dinosaurs of the type that comes to mind if someone says Brontosaurus. A giant sauropod called Alamasaurus, dating to the same period, had been discovered "very close to the site . . . and they thought it was that."
But Jim Madsen, the former state paleontologist, recognized the bones as a theropod, a meat-eater. Scott Sampson, curator of vertebrate paleontology at the museum, studied a skull fragment and realized it had the same distinctive bulge behind the eye socket that T. rex had.
Also, the vertebrae have a shape typical of those of theropods, not shared by plant-eaters.
"It is either Tyrannosaurus rex or it's something that hasn't been described," Sampson said in a telephone interview from his office.
"I can say with confidence that it falls within the size range of the largest Tyrannosaurus. We're talking about a very large, multi-ton animal that without doubt was the dominant carnivore of that time."
Another meat-eater, the Allosaurus, is relatively common in Utah. But it is from an earlier period called the Jurassic.
By strata studies, scientists know this fossil is from the last of the Cretaceous era, 65 million years ago, when the age of the dinosaurs ended. The only large North American carnivore known from that period is the T. rex. So it's either that or some new monster just as ferocious.
Once paleontologists realized they had an important find, they obtained an excavation permit and Getty led the dig.
As he helped chart the location of a bulging vertebra, Loewen said he hopes they will find more than the 40 bones and fragments already uncovered.
"I like to reconstruct in my mind what it was like back then, but mostly while I'm digging, it's just like digging treasure," Loewen added. "You never know what you're going to uncover."
Many of the bones were eroded by underground "pipes," natural tunnels where water percolated through the formation. Others are better preserved.
"We really are not sure what we'll find in this site," Getty said. Possibly many more bones are in the hillside, but it's also possible that most have been eroded away.
They pack burlap-and-plaster jackets around the specimens, so they will be safe when shipped to the U.
Getty said he often thinks about what life was like here, 65 million years ago.
"It's totally, 100 percent, different than it was at the time this animal would have been walking around here. This would have been a coastal plain lowland area with subtropical sorts of vegetation, most likely. And now it's an exposure of dry, semiarid outcrop in a high mountainous area."
So far, they have uncovered bones from the head, pelvis, tail, feet, legs and ribs. One jacket covered a pair of vertebrae that were still connected, weighing 80 pounds.
How will he get it out? "On my back," said Getty.
Even individual bones are heavy. "This is a very large individual. Every bone we've seen has shown us it's a very large individual," he said.
Most of the cleaning, study and reconstruction will take place at the museum's lab, located on the U. campus.
"To me, it's kind of a privilege," working on the site, Getty said. "You know, whatever this is, it's very important."
This will be the first large meat-eating dinosaur from this period ever found in Utah, he marveled. "It's pretty exciting to be involved."
E-mail: bau@desnews.com